JP2000035828A - Power supply circuit and power amplifier using the circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the malfunction and destruction of an IC and the deterioration of a distortion factor when power supply voltage is made to follow the high frequency of the output of an object to be driven. SOLUTION: The inclination of an output signal ZS of an object 14 to be driven is detected by an inclination detection circuit 11, afterwards is sequentially subjected to half-wave rectification and smoothing and is further applied to an addition circuit 12B. Also, the signal ZS undergoes half-wave rectification and after that, it is applied to the circuit 12B. The circuit 12B selects the higher one between two input signals and then superimposes it upon offset. Power supply voltage +Vcc is controlled by power supply voltage +Vc in accordance with a control signal from the circuit 12B and is applied to the object 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power amplifying device suitable for use in audio equipment.

[0002]

2. Description of the Related Art FIG. 5 shows a power amplifying device which is well known in the art and is mounted on a subordinate integrated circuit while a fixed voltage is applied as a power supply voltage. The circuit of FIG.
It has a power supply circuit having a transformer 1 and a bridge circuit 2 and an amplification section including a preamplifier and a power output stage transistor, and amplifies an input signal AS and outputs it to a speaker SP. These are implemented on a hybrid integrated circuit. According to this circuit, after an AC voltage is applied from an AC power supply (not shown) to the transformer 1, the AC voltage is applied to the bridge circuit 2, where it is rectified and applied to the preamplifier 3 using the power supply voltage ± Vcc. . Using this power supply voltage ± Vcc, the preamplifier 3 amplifies the voltage of the input signal AS, and the power output stage transistors Q1 and Q2 further amplify the current to generate an amplified signal ZS.
Drives the speaker SP.

[0003]

In the power amplifier of FIG. 5, the power supply voltage ± Vcc always applies a fixed high voltage corresponding to the maximum output so that the maximum output signal from the amplifier is not clipped. Needed. However,
When the volume is maximized and the output of the amplifier is maximized, the fixed power supply voltage ± Vcc is efficiently consumed as shown in FIG. 6A. However, when the volume is reduced and the output of the amplifier is reduced. As shown in FIG. 6, the power loss increases as shown in FIG.
The cc consumption efficiency was reduced. In a normal use state of the power amplifying device, a large output is rarely required, and the output signal of the amplifying unit is often set to a small or medium level.

Therefore, it has been proposed to use a power supply circuit that changes the power supply voltage ± Vcc so as to follow the output signal of the amplifier. However, according to this proposal, when the output signal of the amplifying unit has a high frequency, the power supply voltage also changes at a high frequency, which adversely affects the IC constituting the amplifying unit. In particular, there has been a problem that the high frequency of the power supply voltage causes a malfunction or destruction of the IC element and a deterioration in the distortion factor of the signal waveform of the amplifier.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a power supply circuit for generating a power supply voltage based on an output signal of a driving target, a gradient detecting circuit for detecting a gradient of the output signal of the driving target, and the gradient detecting circuit. A first rectifier circuit for rectifying the output signal of the first rectifier circuit, a smoothing circuit for smoothing the output signal of the first rectifier circuit, a second rectifier circuit for rectifying the output signal of the drive target, and an output signal of the smoothing circuit or A power supply voltage generation circuit that controls the external power supply according to an output signal of a rectifier circuit to generate a power supply voltage of the drive target.

In particular, the first and second rectifier circuits are characterized by comprising a half-wave rectifier circuit. The power supply circuit further includes an adder circuit for selectively adding an output signal having a high absolute value level from the output signal of the smoothing circuit or the output signal of the second rectifier circuit and applying the added signal to the power supply voltage circuit.

According to another aspect of the present invention, in a power amplifying apparatus having an output amplifying circuit for amplifying an input signal, a gradient detecting circuit for detecting a gradient of an output signal of the output amplifying circuit, and rectifying an output signal of the gradient detecting circuit. A first rectifying circuit, a smoothing circuit for smoothing an output signal of the first rectifying circuit, a second rectifying circuit for rectifying an output signal of the output amplifying circuit, and an output signal of the smoothing circuit or an output of the rectifying circuit. A power supply voltage generation circuit that controls an external power supply according to a signal to generate a power supply voltage of the output amplification circuit.

[0008] Further, there is provided an adding circuit for selectively adding an output signal having a high absolute value level from the output signal of the smoothing circuit or the output signal of the half-wave rectifier circuit, and applying the added signal to the power supply voltage circuit. I do.

In particular, the first and second rectifier circuits are characterized by comprising a half-wave rectifier circuit. Further, in the addition circuit, an offset is superimposed on the output.

Further, the output amplifier, the gradient detection circuit, the first and second rectifier circuits, the smoothing circuit, and the power supply voltage generation circuit are mounted on a hybrid integrated circuit. Features.

According to the present invention, when the output signal of the output amplifier circuit has a low frequency, the output level from the gradient detection circuit is small and the output signal of the smoothing circuit is small, so that the power supply voltage following the waveform is reduced. Generated. When the output signal of the output amplifier circuit has a high frequency, a large-level output signal is generated from the gradient detection circuit, so that the power supply voltage is at a constant level.

[0012]

FIG. 1 is a diagram showing an embodiment of the present invention. Reference numeral 11 denotes an output signal ZS to be driven, which will be described later.
An offset setting unit 12a for setting an offset for determining a minimum voltage of the power supply voltage + Vc based on the external power supply voltage + Vcc;
A voltage control circuit comprising a signal obtained by processing the output signal of the gradient detection circuit 11 and an addition circuit for adding an offset;
Is a power supply voltage + Vc according to a control signal of the voltage control circuit 12.
a power supply voltage generator for generating a power supply voltage + Vc from the power supply voltage c;
Is a driving target constituted by a power amplifier as in a conventional example, 15 is a diode forming a half-wave rectification circuit for half-wave rectifying an output signal of the driving target 14, and 16 is a half-wave rectification of an output signal of the gradient detection circuit 11. And 17 is a smoothing capacitor for smoothing the output signal of the diode 16. Note that, except for the drive target 14, a power supply circuit is configured by the above-described circuits, and all the circuits in FIG. 1 are mounted on a hybrid integrated circuit.

In FIG. 1, an output signal Z of a driving object 14 is shown.
S is detected by the gradient detection circuit 11 whether the gradient or the gradient is steep or gentle.

When the output signal ZS has a high frequency as shown in FIG. 2ZS, the gradient of the output signal ZS becomes steep, so that the output level of the gradient detection circuit 11 becomes high as shown by the dotted line in FIG. 2A. Further, since the gradient detection circuit 11 is constituted by, for example, a differentiation circuit, the phase of the output signal of the gradient detection circuit 11 is advanced by, for example, 45 degrees as compared with the signal ZS due to its characteristics. The output signal of the gradient detection circuit 11 is half-wave rectified by the diode 16 and then smoothed by the smoothing capacitor 17. Therefore, the output voltage A from the smoothing capacitor 17 is as shown by the solid line in FIG. 2A. The advance of the output phase of the gradient detection circuit 11 changes according to the characteristics of the differentiating circuit.

The output signal ZS of the driven object 14 is half-wave rectified by the diode 15 to have a waveform as shown in FIG. 2B. On the other hand, in the offset setting unit 12A, a predetermined level offset is generated from GND as shown in FIG. 2C based on the power supply voltage + Vcc. Then, the addition circuit 12B
In the above, a signal having a high level among the signal A from the smoothing capacitor 17 or the signal B from the diode 15 is
The output is superimposed on the offset as shown in FIG. 2D. Further, the output signal D of the adding circuit 12B is applied to the power supply voltage generation circuit 13 as a control signal, and an external power supply voltage + Vcc is generated based on the control signal D. As a result, the power supply voltage + Vcc is at a substantially constant level as shown in FIG. 2E.

Next, the output signal ZS of the driven object 14 is shown in FIG.
The case of low frequency as described above will be described. When the output signal ZS has a low frequency, the gradient of the output signal ZS becomes gentle,
As shown in FIG. 2A ', the output level of the gradient detection circuit 11 is low. The phase of the output signal of the gradient detection circuit 11 is the signal Z.
For example, it is advanced by 90 degrees compared to S. The output signal of the gradient detection circuit 11 is half-wave rectified by the diode 16 and then smoothed by the smoothing capacitor 17. However, since the output signal of the gradient detecting circuit 11 changes slowly, the output voltage A of the smoothing capacitor 17 follows the output of the gradient detecting circuit 11 as shown in FIG. 2A '.

The output signal ZS of the driven object 14 is half-wave rectified by the diode 15 to have a waveform as shown in FIG. 2B '. Then, in the adder circuit 12B, a high-level signal of the signal A 'from the smoothing capacitor 17 or the signal B' from the diode 15 is superimposed on the offset and output. Therefore, the output signal D 'of the adding circuit 12B
Follow a half-wave rectified waveform as shown in FIG. 2D '.
The power supply voltage generation circuit 13 is controlled according to the control signal D 'from the addition circuit 12B, and as a result, the power supply voltage + Vc
Follow the output signal ZS of the drive target 14 as shown in FIG. 2E '.

By the above operation, the power supply voltage +
Vc follows the output signal ZS of the drive target 14 at a low frequency, and becomes a substantially constant voltage corresponding to the amplitude of the output signal ZS at a high frequency.

Therefore, when the output signal ZS of the driven object 14 has a high frequency, it is possible to prevent a change in the power supply voltage from delaying the phase of the output waveform of the driven object 14. Each element such as a transistor can prevent malfunction, destruction, and deterioration of the distortion rate of the output signal ZS. Since the power supply voltage + Vc corresponds to the amplified signal ZS, a large increase in the loss voltage can be prevented. on the other hand,
When the signal ZS has a low frequency, the power supply voltage + Vc is equal to the signal ZS.
Since the waveform of S is followed, the loss voltage of the driven object 14 can be reduced.

In FIG. 1, a circuit having the same function as that of the power supply circuit 20 is also connected to the negative power supply side of the drive target 14, and the circuit is omitted for simplification of description. Since the circuit is also connected to the negative power supply, the power supply voltage −V
c follows the output signal ZS of the drive target 14 at a low frequency, and becomes a substantially constant voltage at a high frequency. Further, the power supply circuit 20 of FIG. 1 can be applied to a single power supply as well as a positive / negative power supply.

FIG. 4 is a specific circuit example of the power supply circuit 20 of FIG. In order to simplify the circuit description, only the positive power supply will be described, and the negative power supply will be omitted.

First, in FIG. 4, the external power supply voltage + Vc
c is applied to the cathode of the Zener diode ZD01, and the Zener diode ZD01 operates to generate the inter-terminal voltage Vzd01. Voltage Vzd01
Is divided by the resistors R01 and R02. The divided voltage V1 is applied to the transistor TR02 and the transistor TR0
The difference between the base voltage and the emitter voltage of the transistor T
Since the voltage becomes higher than the base-emitter voltage Vbe02 of R02, the transistor TR02 operates. When the transistor TR02 is turned on, a current flows through the resistor R05. As a result, the voltage V2 is generated by the voltage drop of the resistor R05, and the voltage V2 is applied as an offset to the base of the transistor TR03.

The output signal ZS of the driven object 14 is differentiated by a differentiating circuit (gradient detecting circuit) 11 composed of a capacitor C01 and a resistor R09, and then half-wave rectified by a diode D02. After the output voltage from the diode D02 is smoothed by the smoothing capacitor C02, the output voltage is applied to the base of the transistor TR04 serving as an emitter follower circuit.

On the other hand, the output signal ZS is half-wave rectified by the diode D01, and then the output voltage DS from the diode D01.
01 is divided by the resistors R07 and R08. At the emitter of the transistor TR05, the transistor TR05
Or the higher of the divided voltages of the resistors R07 and R08 is applied to the base of the transistor TR04. The base voltage of the transistor TR04 is level-shifted by the base-emitter voltage Vbe04 of the transistor TR04, and is superimposed on the voltage V2 corresponding to the voltage drop of the resistor R05.
Applied to the base of R03.

Further, after the base voltage of the transistor TR03 is level-shifted in the direction of increasing by the base-emitter voltage Vbe03, the control transistor T03
Applied to the base of R01. Therefore, power supply voltage + Vc is generated from external power supply voltage + Vcc in control transistor TR01.

In FIG. 4, since the output signal of the differentiating circuit 11 for differentiating a signal swinging positively and negatively is subjected to half-wave rectification, the differentiating circuit 11 can be used for both positive and negative power supplies.

[0027]

According to the present invention, when the output signal of the driven object has a high frequency, it is possible to prevent the output of the driven object from being delayed due to the power supply voltage being substantially constant voltage. Each element can prevent malfunction, destruction and deterioration of signal distortion rate, and when the frequency becomes low, the power supply voltage follows the output waveform of the driven object, so that the loss voltage of the driven object can be reduced. .

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is a waveform diagram showing output waveforms of respective elements of the power supply circuit 20 of FIG.

FIG. 3 is a waveform diagram showing an output waveform of a driving target in FIG. 1;

FIG. 4 is a circuit diagram showing a specific circuit of the power supply circuit 20 of FIG.

FIG. 5 is a circuit diagram showing a conventional example.

FIG. 6 is a waveform diagram showing a relationship between an output waveform and a power supply voltage in a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Slope detection circuit 12 Voltage control circuit 12A Offset setting unit 12B Addition circuit 13 Power supply voltage setting circuit 14 Driving target

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Satoshi Sugimoto 2-5-5 Keihanhondori, Moriguchi-shi, Osaka F-term in Sanyo Electric Co., Ltd. 5H420 CC02 DD02 EA10 EA21 EA44 EA47 EB37 FF03 FF25 5H430 BB09 CC01 CC05 EE02 EE03 EE14 FF03 FF13 LA12 5J092 AA02 AA18 AA41 AA58 CA21 CA36 CA57 FA02 GR01 GR05 HA02 HA08 HA19 HA20 HA25 HA29 KA11 KA26 KA30 KA48 KA51 KA55 MA20 MA24 SA05 TA01 TA06

Claims (8)

[Claims] 1. A power supply circuit for generating a power supply voltage based on an output signal of a drive target, a gradient detection circuit detecting a gradient of the output signal of the drive target, and a first rectifying an output signal of the gradient detection circuit. A rectifier circuit, a smoothing circuit for smoothing an output signal of the first rectifier circuit, a second rectifier circuit for rectifying the output signal of the drive target, and an output signal of the smoothing circuit or an output signal of the rectifier circuit. A power supply circuit for controlling the external power supply to generate a power supply voltage of the drive target. 2. The power supply circuit according to claim 1, wherein said first and second rectifier circuits comprise half-wave rectifier circuits. 3. An apparatus according to claim 1, further comprising an adder circuit for selectively adding an output signal having a high absolute value level from the output signal of the smoothing circuit or the output signal of the second rectifier circuit, and applying the added signal to the power supply voltage circuit. The power supply circuit according to claim 1, wherein: 4. A power amplifying device having an output amplifying circuit for amplifying an input signal, a gradient detecting circuit for detecting a gradient of an output signal of the output amplifying circuit, and a first rectifier for rectifying an output signal of the gradient detecting circuit. A smoothing circuit for smoothing an output signal of the first rectifying circuit; a second rectifying circuit for rectifying an output signal of the output amplifying circuit; and an output signal of the smoothing circuit or an output signal of the rectifying circuit. A power amplification device comprising: a power supply voltage generation circuit that controls an external power supply to generate a power supply voltage of the output amplification circuit. 5. An addition circuit for selecting and adding an output signal having a high absolute value level from an output signal of the smoothing circuit or an output signal of the half-wave rectifier circuit, and applying the added signal to the power supply voltage circuit. The power amplifying device according to claim 5, characterized in that: 6. The power amplifying device according to claim 4, wherein said first and second rectifier circuits comprise half-wave rectifier circuits. 7. The power amplifying device according to claim 6, wherein an offset is superimposed on an output of said adding circuit. 8. The output amplifier, the gradient detection circuit, the first and second rectifier circuits, the smoothing circuit, and the power supply voltage generation circuit are mounted on a hybrid integrated circuit. The power amplifying device according to claim 4, characterized in that: